1. Technical Field
The present invention relates to a webbing winder which winds a webbing belt for restraining a body of a passenger.
2. Related Art
As disclosed in, for example, Japanese Patent Application Laid-open (JP-A) No. 5-193441, a webbing winder constituting a seat belt device for a vehicle is provided with a lock mechanism which restricts rotation of a reel shaft in a withdrawal direction during rapid deceleration of the vehicle. A lock gear constituting the lock mechanism disclosed in JP-A No. 5-193441 can be relatively rotated coaxially with the reel shaft. When the reel shaft is rotated relatively to the lock gear in the withdrawal direction, teeth of each of a main pawl and a backup pawl mesh with inner teeth formed on both side walls of a frame in association with the relative rotation, thereby restricting the rotation of the reel shaft in the withdrawal direction. There are two types of configurations which generate the relative rotation between the reel shaft and the lock gear. One of the two configurations is deceleration detecting means. The deceleration detecting means is provided with an inertial member which makes an inertial movement during the rapid deceleration of the vehicle, and therefore, a lock pawl pushed up by the inertial member which makes the inertial movement meshes with outer teeth of the lock gear, thereby restricting the rotation of the lock gear, so as to allow the lock gear to be rotated relatively to the reel shaft which is rotated in the withdrawal direction.
The other configuration which generates the relative rotation between the reel shaft and the lock gear is another inertial member disposed in the lock gear independently of the inertial member of the deceleration detecting means. This inertial member is connected to the lock gear via a spring. When the lock gear is rapidly rotated in the withdrawal direction together with the reel shaft, the inertial member generates a rotational delay with respect to the lock gear against an urging force of the spring due to the inertia. The inertial member is moved outward in a rotationally radial direction of the lock gear simultaneously with the rotation relative to the lock gear owing to the rotational delay, to mesh with a ratchet gear of an inner gear formed inside of a cover, thereby stopping the rotation of the inertial member, and further, the lock gear. Thus, the rotation of the lock gear is stopped, so that the lock gear is rotated relatively to the reel shaft which is rotated in the withdrawal direction.
Here, if a lock mechanism is accidentally operated immediately after a webbing belt is completely wound by the reel shaft, the reel shaft is put into a so-called “end lock state,” in which it cannot be rotated in this state in the withdrawal direction. Since the reel shaft cannot be rotated in the withdrawal direction in this end lock state, the webbing belt is hardly drawn. As a consequence, the webbing winder is configured such that the lock pawl of the deceleration detecting means cannot mesh with the outer teeth of the lock gear when the webbing belt is completely wound in the above-described JP-A No. 5-193441, thus avoiding the end lock state.
However, if a spool is rotated rapidly and slightly in the withdrawal direction in reaction immediately after the webbing belt is completely wound, the inertial member disposed in the lock gear accidentally meshes with the ratchet gear formed at the cover. In this state, if the spool is rotated in the withdrawal direction to draw out the webbing belt, the lock mechanism is undesirably operated so as to be put into the end lock state.